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Hybrid fitting-numerical method for determining strain-hardening behavior of sheet metals


Quoc Tuan Pham*, Trung Nguyen-Thoi, Jinjin Ha, Young-Suk Kim

Source title: 
Mechanics of Materials, 161: 104031, 2021 (ISI)
Academic year of acceptance: 

The uniaxial tensile test is well-established for experimentally identifying the stress–strain relationship for sheet metals. Conventionally, true stress–strain data obtained from the test are used to identify the hardening law's parameters using the curve-fitting method. Extrapolation using the identified hardening law describes the stress–strain relationship at large strains; however, it varies widely, depending on the selection of hardening models and their identified parameters. This study presents a hybrid method incorporating the curve-fitting method and inverse finite element analysis to identify the Kim–Tuan hardening model's parameters over large strain ranges. Here, the curve-fitting method enforces the identified hardening law's accuracy in the pre-necking range. Simultaneously, the inverse finite element analysis method maintains the goodness of the post-necking prediction. The proposed method is used to calibrate hardening laws for DP780 and AA6016-T651 sheet metals subjected to uniaxial tensile tests at room and warm temperatures, respectively. The calibrated hardening laws capture the force–displacement curves of both materials well, validating the ability of the presented method in practice.